Method for controlling an aerodyne for the vertical avoidance of a zone

ABSTRACT

A method of automatically controlling an aircraft to avoid a vertical zone includes several steps. The aircraft first acquires limits of the zone to be avoided. The zone is modeled by a cylindrical volume which is limited by a horizontal contour with upper and lower altitudes of the zone. The cylindrical volume associated with a scheduled route of the aircraft is located and points of entry and exit in the cylindrical volume are determined. A new flight altitude is calculated in order to avoid the zone. A point of change of altitude is calculated to reach an avoidance altitude. The new flight altitude is updated and the point of change of altitude is input into an automatic pilot.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for automatically controllingan aerodyne permitting the vertical avoidance of a zone, for example adangerous weather zone or one in which there is a risk of the comfortand safety of the flight being affected.

2. Discussion of the Background

It applies in particular, but not exclusively, to the avoidance of aninvisible zone, for example one of strong turbulence, such as clear airturbulence, or one in which the risk of icing is considerable. This zoneis roughly delimited by a horizontal contour of large dimensions andupper and lower vertical limits. Such information is, for example,received by the aerodyne by way of a digital data transmission device,for example Data-Link, and has been sent by a ground station, possiblybased on information transmitted by the neighbouring aerodynes equippedwith an ADS (Automatic Dependent Surveillance) system.

Currently, it is up to the pilot to handle the meteorological problemmanually, either by carrying out avoidance within sight of the zone, orby taking the risk of traversing the zone, these operations having totake account of a considerable number of parameters, and in particular,of the regulations in force within the air space traversed, of theperformance of the aerodyne, and of the weight of fuel in its tanks.Moreover, given that the so-called clear weather meteorologicalphenomena are by definition invisible, it frequently happens that thepilot is warned of such a phenomenom only a very short time beforeentering the zone in which this phenomenom is located, and in manycases, this time is insufficient to enable him to take into account allthe necessary parameters for determining the best avoidance trajectory.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome this drawback and toease the pilot's task. For this purpose, it proposes a method forautomatically controlling an aerodyne for the vertical avoidance of afixed zone with predefined geometrical contours, the aerodyne beingequipped with an automatic piloting device, into which have been input ascheduled route, a cruising flight altitude and the position of thepoint of descent towards the scheduled runway.

According to the invention, this method is characterized in that itcomprises the following steps in succession:

the acquiring of the limits of the zone to be avoided in the form of ahorizontal contour and upper and lower altitudes, and the modelling ofthe zone to be avoided by a cylindrical volume delimited by thehorizontal contour and the upper and lower altitudes,

the locating of the cylindrical volume with respect to the scheduledroute of the aerodyne so as to determine whether this route traversesthe cylindrical volume,

if the scheduled route traverses the cylindrical volume, the determiningof the points of entry and of exit of the scheduled route in thecylindrical volume,

the calculating of the optimum and maximum altitudes capable of beingreached by the aerodyne, and of the weight of the latter when passingthrough the point of entry, account being taken of the current weight ofthe aerodyne, and of its consumption of fuel in order to reach thispoint,

the calculating of a new flight altitude for the vertical avoidance ofthe zone, and of a point of change of altitude so as to reach theavoidance altitude, as a function of the altitudes of the lower andupper limits of the zone, of the current, maximum and optimum altitudesof the aerodyne, and of the position of the scheduled points of exitfrom the cylindrical volume and of descent of the aerodyne, and

the updating of the new flight altitude, and the inputting of theposition of the point of change of altitude into the automatic pilotingdevice.

By virtue of these provisions, the burden of modifying the flight planand of controlling the aerodyne with a view to avoiding the dangerouszone is completely removed from the pilot.

According to a particular feature of the invention, the avoidance of thezone is performed by flying below when the upper altitude of the zonelies above the maximum altitude capable of being reached by the aerodyneat the point of entry, or else when the scheduled point of descent liesin the cylindrical volume.

According to another particular feature of the invention, the avoidancealtitude is preferably equal to the optimum altitude of the aerodyne atthe point of entry.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the method according to the invention will be describedhereinafter, by way of a non-limiting example, with reference to theappended drawings in which:

FIG. 1 diagramatically represents the electronic equipment of anaerodyne comprising a computer intended to implement the methodaccording to the invention;

FIG. 2 diagramatically represents in perspective the trajectory of anaerodyne which traverses a cylindrical volume enveloping a zone to beavoided;

FIG. 3 shows a section through a vertical plane of the initiallyscheduled trajectory of the aerodyne, and the possible avoidancetrajectories, with respect to the cylindrical volume enveloping the zoneto be avoided; and

FIGS. 4, 5a and 5b diagramatically illustrate the algorithm executed inorder to process the information relating to the limits of a zone to beavoided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As represented in FIG. 1, the avoidance method according to theinvention is particularly designed to be executed by a computer 4installed on board an aerodyne, which is coupled by way of a datatransmission bus 5, called the "aircraft bus", to the navigationequipment which includes an automatic piloting device 14 and navigationinstruments 16, to a digital data transmission device 15, for exampleData-Link, and also to a man/machine interface device (MMI) 6 comprisinga control element and signalling elements, such as a display screen 7and a loudspeaker 8 which are installed in the cockpit.

In a known manner, the automatic piloting device 14 comprises a memoryin which is recorded the aerodyne's scheduled trajectory comprising alateral trajectory and a vertical profile. The lateral trajectoryconsists of a route formed of a succession of straight segments betweenthe departure point and the destination point, and of transitiontrajectories making it possible to join one segment to another. Thevertical profile indicates in particular the cruising altitude and theposition of the point of descent towards the scheduled runway.

The data transmission device 15, consisting for example of a Data-Linkcommunication system, is capable of receiving meteorological informationfrom a ground station or from aerodynes situated within radio range.This information makes it possible to locate a zone of meteorologicalactivity, for example, in which there is strong turbulence orconsiderable icing conditions.

When such information is received, the computer 4 executes the algorithmshown in FIG. 4. This algorithm consists firstly, in step 21, inacquiring the data delivered by the data transmission device 15 and indelimiting a meteorological zone by a cylindrical volume 10 defined by ahorizontal contour and lower and upper altitudes (FIG. 2).

In step 22 of FIG. 4, the computer 4 locates the route 2 defined in FIG.2 by the scheduled flight plan of an aerodyne 1, with respect to themeteorological zone. To do this, the computer 4 accesses the definitionof the scheduled flight plan which is for example stored in theautomatic piloting device 14.

If the aerodyne 1 is not going to enter the meteorological zone, onereturns to the start 20 of the algorithm to continue the analysis of theinformation supplied by the data transmission device 15. In the contrarycase, in step 23 in FIG. 4, the computer 4 sends a message intended forthe display screen 7 so as to warn the pilot that the route 2 to betravelled by the aerodyne 1 traverses a zone of meteorological activity.This information can be supplemented by the displaying on the screen 7of the map of the overflown region, overlaid with the limits of thezone.

It is then required to determine an avoidance trajectory such asA1-A2-A3-A4 which passes above the cylindrical volume 10 or B1-B2-B3-B4which passes below the cylindrical volume 10, these being shown in FIG.3. These trajectories are defined by a point of exit A1, B1 from theinitially scheduled trajectory, a phase of change of altitude A1-A2,B1-B2 so as to meet up with the avoidance altitude, and a constantaltitude phase A2-A3, B2-B3 at the avoidance altitude, and a descentphase of return to the scheduled trajectory A3-A4, B3-B4 and a point ofreturn A4, B4 to the scheduled trajectory.

It should be noted that, in certain cases, this point of return may lieafter the initially scheduled point of descent T, the avoidancetrajectory meeting up directly with the descent trajectory 2' at theavoidance altitude.

In step 24, the computer 4 triggers the determination of an avoidancetrajectory. During this step, it therefore determines in particular theavoidance altitude, a computational algorithm example of which isrepresented in FIGS. 5a and 5b and the point of exit A1, B1 from thescheduled trajectory so as to reach the specified avoidance altitude(FIG. 3).

This point is calculated by taking account of the characteristics of theaerodyne, of the air regulations which define a maximum rate of climb orof descent, as well as of the discrepancy between the current altitudeof the aerodyne 1 and the avoidance altitude to be reached.

In step 25, the computer 4 waits for the confirmation by the pilot ofthe new flight plan including the avoidance trajectory specified in step24, doing so until the point of exit A1, B1 from the initially scheduledroute 2 has been passed (step 26). While waiting, the computer 4computes and displays the value of the distance of this point of exitA1, B1, having regard to the current position of the aerodyne 1, thisvalue being periodically refreshed (step 27).

If, during this wait, the pilot has confirmed the new flight plan, thelatter is sent to the automatic piloting device 14 in replacement forthat route 2 initially scheduled, which then becomes active (step 28).The computer 4 then stands by again for new information in step 21.

If the pilot has not confirmed the new flight plan before crossing thepoint of exit A1, B1, in step 29 the computer 4 sends a message to thepilot to indicate that this point of exit A1, B1 has been passed andthat avoidance of the zone is now impossible. Next, in step 30, itcomputes the distance between the current position of the aerodyne 1 andan entry point Z into the zone delimited by the cylindrical volume 10.So long as the aerodyne 1 has not reached entry point Z, this distanceis displayed with periodic refreshing (step 31). After this entry pointZ has been crossed, the computer 4 sends an alert message which signalsto the pilot that the aerodyne 1 is in the meteorological zone (step32). The computer 4 then waits for the zone delimited by the cylindricalvolume 10 to be exited, having regard to the position of the point ofexit Z' from this zone, and also to the current position and to thespeed of the aerodyne 1 (step 33), before returning to step 21 foracquiring data, with erasure of the alert message.

In FIG. 5a, the determination of the avoidance altitude begins with thecalculation of the position of the point of entry Z into the zone to beavoided, as well as of the distance separating this entry point Z fromthe current position of the aerodyne 1 and of the weight of the latterat this point, account being taken of the current weight and of the fuelconsumption of the aerodyne 1 (step 41).

In step 42, the computer 4 determines the optimum (alt.opti) and maximum(alt.max) altitudes of the aerodyne 1 at the point Z, account beingtaken of the weight and performance of the aerodyne 1, as well as to thedistance separating the aerodyne from this point Z. If the altitude ofthe upper limit of the zone to be avoided (alt.upp.zone) is not greaterthan the maximum altitude (alt.max) which the aerodyne 1 can reach atthe entry point Z (step 43), the computer 4 goes to step 58 representedin FIG. 5b. Otherwise, upper avoidance (above the zone) is impossibleand hence lower avoidance (below the zone) is compulsory, and thecomputer 4 goes to step 44 in FIG. 5a in which it checks whether thealtitude (alt.low.zone) of the lower limit of the zone to be avoidedsatisfies conditions which depend on the original altitude given by theoriginal flight plan and on the minimum permitted altitude (alt.min).This minimum altitude may either be of regulatory origin, such as theMEA (Minimum Enroute Altitude) and MORA (Minimum Offroute Altitude)altitudes, or be of operational origin (Minimum Operational Altitudewhich corresponds to the regulatory flight level above the FL195 levelfor example).

For example, the altitude of the lower limit of the zone must be greaterthan the minimum permitted altitude, and must be greater than a value(alt.D) obtained by subtracting a certain predetermined value from theinitial altitude.

If the altitude of the lower limit of the zone does not satisfy theseconditions, automatic avoidance of the zone is impossible and processingcontinues from step 29. Otherwise, the computer 4 checks in step 45whether the altitude of the lower limit of the zone (alt.low.zone) isgreater than the optimum altitude (alt.opti) calculated in step 42. Ifsuch is the case, the avoidance altitude to be met up with (alt.avoid)corresponds to the optimum altitude (step 46), and if not the avoidancealtitude lies just below the zone, calculated with a certain safetymargin (step 47).

The ensuing algorithm consists in determining the landing descent startpoint.

To do this, in step 48 the computer 4 determines the position of thepoint of exit Z' of the scheduled route 2 from the cylindrical volume10, and the distance between this point and the scheduled point T ofdescent towards the runway. If this distance is greater than a thresholdvalue, for example 100 nautical miles, it signifies that the aerodyne 1can meet up with the point of descent T at the scheduled altitude (step50). Otherwise, the aerodyne 1 should not meet up with this point ofdescent T, but will remain at the previously calculated avoidancealtitude until it meets up with the descent trajectory 2' of thescheduled route. The computer 4 then determines the new point of descentT' or T" which corresponds to the point at which the (lower or upper)avoidance trajectory at the avoidance altitude meets the initiallyscheduled descent trajectory 2' (step 51). On completing steps 50 and51, execution continues via step 25.

If in step 43, the upper altitude (alt.upp.zone) of the zone is lessthan the maximum altitude (alt.max) calculated in step 42 which theaerodyne 1 can reach, in step 58 the computer 4 determines whether thescheduled point of descent T does or does not lie in the zone, bycomparing the distances between the current position of the aerodyne 1and the points Z' and T (FIG. 5b). If the point T lies inside the zone,upper avoidance is not possible and the computer 4 carries out a loweravoidance calculation by going to step 59 where it checks whether loweravoidance is possible. Otherwise, in step 60 the computer determineswhether lower avoidance is possible by comparing the lower altitude(alt.low.zone) of the zone with the minimum permitted altitude(alt.min), as well as with the value (alt.D) (obtained by subtracting acertain predetermined value of the altitude given by the original flightplan). If lower avoidance is impossible, avoidance is performed bypassing above the zone.

If avoidance is possible by flying above and below the zone, and if thecurrent altitude (alt.aircraft) of the aerodyne 1 is less than theoptimum altitude (alt.opti) (step 64), then upper avoidance is carriedout, otherwise lower avoidance is carried out.

In step 59, upper avoidance is not possible and the computer examineswhether lower avoidance is possible by comparing, as already described,the lower altitude (alt.low.zone) of the zone 10 with the minimumaltitude values (alt.min and alt.D). If lower avoidance is impossible,processing continues from step 29.

In order to carry out an upper avoidance following steps 60 or 64, thecomputer 4 compares the optimum altitude (alt.opti) with the upperaltitude (alt.upp.zone) of the zone (step 65). If the optimum altitudeis greater than the upper altitude of the zone, the avoidance altitude(alt.avoid) corresponds to the optimum altitude (alt.opti) (step 66),otherwise, the avoidance altitude corresponds to the upper altitude(alt.upp.zone) of the zone with a safety margin (step 67). Execution ofthe algorithm continues via step 48 in order to determine the positionof the point of descent T or T" towards the runway.

Similarly, in order to carry out a lower avoidance following steps 59 or64, the computer 4 examines whether the optimum altitude (alt.opti) isnot less than the lower altitude (alt.low.zone) of the zone (step 68),the avoidance altitude (alt.avoid) corresponds to the lower altitude ofthe zone with a safety margin (step 69), otherwise it corresponds to theoptimum altitude (step 70).

The computer then goes to step 48 described hereinabove in order todetermine the point of descent T or T' towards the runway.

In practice, the altitude to be complied with by the aerodyne 1 iscalculated in the form of a flight level, the flight levels being spacedapart by 100 feet (30.48 m). Thus, in step 42, the computer 4 alsodetermines the optimum, respectively maximum, flight levels, by roundingthe calculated altitudes to the nearest, respectively lower, flightlevel. In step 43, the upper altitude of the zone is in fact comparedwith the maximum flight level. In steps 44 and 60, the lower altitude ofthe zone is compared with the value (alt.D) obtained by subtracting theheight of three flight levels, for example, from the initially scheduledflight level, as well as with the minimum flight level FL 195.

Likewise, the avoidance altitude is calculated in terms of flight leveland the margin used in steps 47, 67 and 69 corresponds to a flightlevel.

What is claimed is:
 1. Method for automatically controlling an aerodynefor vertical avoidance of a zone to be avoided with predefinedgeometrical contours, said aerodyne being equipped with an automaticpiloting device, into which have been input a scheduled route and avertical trajectory profile including a cruising flight altitude and aposition of a point of descent towards a scheduled runway, said methodcomprising the following steps in succession:acquiring limits of thezone to be avoided in a form of a horizontal contour with upper andlower altitudes, modelling of the zone to be avoided by a cylindricalvolume delimited by the horizontal contour with the upper and loweraltitudes, locating the cylindrical volume with respect to the scheduledroute of the aerodyne so as to determine whether this route traversesthe cylindrical volume, determining points of entry and of exit of thescheduled route in the cylindrical volume, if the scheduled routetraverses the cylindrical volume, calculating optimum and maximumaltitudes capable of being reached by the aerodyne, and current weightof the aerodyne when passing through the point of entry, account beingtaken of the current weight of the aerodyne and of consumption of fuelin order to reach this point of entry, calculating a new flight altitudefor the vertical avoidance of the cylindrical volume, and of a point ofchange of altitude so as to reach an avoidance altitude, as a functionof the lower and upper altitudes of the horizontal contour of the zoneto be avoided, of current, maximum and optimum altitudes of theaerodyne, and of scheduled points of exit and of descent of theaerodyne, updating the current altitudes of the aerodyne, and inputtingthe point of change of altitude into the automatic piloting device. 2.Method according to claim 1, wherein:avoidance of the zone occurs byflying below the cylindrical volume when the lower altitude of thehorizontal contour of the zone is greater than a certain predeterminedlimit, and when the upper altitude of the horizontal contour of the zonelies above the maximum altitude capable of being reached by the aerodyneat the point of entry into the zone, or else when the scheduled point ofdescent lies in the cylindrical volume.
 3. Method according to claim 2,wherein:said avoidance altitude is preferably equal to the optimumaltitude of the aerodyne at the point of entry.
 4. Method according toclaim 2, furthermore comprising the steps of:periodically calculatingand displaying a distance between a current position of the aerodyne andthe point of exit from the scheduled route towards a selected avoidancetrajectory, and activating a new route incorporating the selectedavoidance trajectory being performed if the latter has been confirmed byan operator.
 5. Method according to claim 2, in the case of an avoidanceby flying below the zone to be avoided, and if the distance between thepoint of exit of the scheduled route from the cylindrical volume and thescheduled point of descent of the aerodyne is less than a predeterminedthreshold, furthermore comprising the step of:calculating a new point ofdescent corresponding to a point at which a selected avoidancetrajectory at the avoidance altitude meets an initially scheduleddescent trajectory.
 6. Method according to claim 2, if avoidance of thezone to be avoided is possible by flying above and below, furthermorecomprising the step of:selecting an avoidance trajectory situated withrespect to the aerodyne in a direction of the optimum altitude. 7.Method according to claim 1, wherein:said avoidance altitude ispreferably equal to the optimum altitude of the aerodyne at the point ofentry.
 8. Method according to claim 7, furthermore comprising the stepsof:periodically calculating and displaying a distance between a currentposition of the aerodyne and the point of exit from the scheduled routetowards a selected avoidance trajectory, and activating a new routeincorporating the selected avoidance trajectory being performed if thelatter has been confirmed by an operator.
 9. Method according to claim3, in the case of an avoidance by flying below the zone to be avoided,and if the distance between the point of exit of the scheduled routefrom the cylindrical volume and the scheduled point of descent of theaerodyne is less than a predetermined threshold, furthermore comprisingthe step of:calculating a new point of descent corresponding to a pointat which a selected avoidance trajectory at the avoidance altitude meetsan initially scheduled descent trajectory.
 10. Method according to claim7, if avoidance of the zone to be avoided is possible by flying aboveand below, furthermore comprising the step of:selecting an avoidancetrajectory situated with respect to the aerodyne in a direction of theoptimum altitude.
 11. Method according to claim 1, furthermorecomprising the steps of:periodically calculating and displaying adistance between a current position of the aerodyne and the point ofexit from the scheduled route towards a selected avoidance trajectory,and activating a new route incorporating the selected avoidancetrajectory being performed if the latter has been confirmed by anoperator.
 12. Method according to claim 11, furthermore comprising thesteps of:periodically calculating and displaying the distance betweenthe current position of the aerodyne and the zone to be avoided, if thepoint of exit has been passed without the new route having beenconfirmed, and displaying a warning message when the aerodyne enters thezone to be avoided.
 13. Method according to claim 12, in the case of anavoidance by flying below the zone to be avoided, and if the distancebetween the point of exit of the scheduled route from the cylindricalvolume and the scheduled point of descent of the aerodyne is less than apredetermined threshold, furthermore comprising the step of:calculatinga new point of descent corresponding to a point at which the selectedavoidance trajectory at the avoidance altitude meets an initiallyscheduled descent trajectory.
 14. Method according to claim 12, ifavoidance of the zone to be avoided is possible by flying above andbelow, furthermore comprising the step of:preliminarily selecting theavoidance trajectory situated with respect to the aerodyne in adirection of the optimum altitude.
 15. Method according to claim 11, inthe case of an avoidance by flying below the zone to be avoided, and ifthe distance between the point of exit of the scheduled route from thecylindrical volume and the scheduled point of descent of the aerodyne isless than a predetermined threshold, furthermore comprising the stepof:calculating a new point of descent corresponding to a point at whichthe selected avoidance trajectory at the avoidance altitude meets aninitially scheduled descent trajectory.
 16. Method according to claim11, if avoidance of the zone to be avoided is possible by flying aboveand below, furthermore comprising the step of:preliminarily selectingthe avoidance trajectory situated with respect to the aerodyne in adirection of optimum altitude.
 17. Method according to claim 1, in thecase of an avoidance by flying below the zone to be avoided, and if thedistance between the point of exit of the scheduled route from thecylindrical volume and the scheduled point of descent of the aerodyne isless than a predetermined threshold, furthermore comprising the stepof:calculating a new point of descent corresponding to a point at whicha selected avoidance trajectory at the avoidance altitude meets aninitially scheduled descent trajectory.
 18. Method according to claim17, if avoidance of the zone to be avoided is possible by flying aboveand below, furthermore comprising the step of:selecting the avoidancetrajectory situated with respect to the aerodyne in a direction of theoptimum altitude.
 19. Method according to claim 1, if avoidance of thezone to be avoided is possible by flying above and below, furthermorecomprising the step of:selecting an avoidance trajectory situated withrespect to the aerodyne in a direction of the optimum altitude. 20.Method according to claim 1, wherein:said zone to be avoided is adangerous meteorological zone, especially one of clear air turbulenceand/or icing.